Manufacturing method of ito powder with tin dissolved in indium oxide, and manufacturing method of ito target

ABSTRACT

The present invention relates to a manufacturing method of ITO powder with tin dissolved in indium oxide, wherein the ITO powder is obtained by performing splay pyrolysis to a mixed solution or slurry of indium nitrate and tin chloride in which the concentration of indium and tin is 3.0 mol/L or more, thereby providing at low costs ITO powder superior in component dispersibility by dissolving tin in indium oxide as well as a precise ITO target superior in uniformity. It is thereby possible to restrain the deterioration of quality or abnormal protrusions such as nodules in cases where the ITO sputtering target deposition is not uniform.

TECHNICAL FIELD

[0001] The present invention relates to the manufacturing method of ITOpowder with tin dissolved in indium oxide used for forming an ITO film(tin oxide—indium oxide), and to the manufacturing method of an ITOtarget.

BACKGROUND ART

[0002] An ITO film is widely used as a transparent electrode (film) of adisplay device; mainly a liquid crystal display. As a method of formingthis ITO film, ordinarily employed is a method generally referred to asa physical vapor deposition method such as the vacuum deposition methodor sputtering method. Particularly, the magnetron sputtering method isoften employed for forming such ITO film from the perspective ofoperability and stability of the film.

[0003] The formation of film with the sputtering method is performed byphysically colliding a positive ion such as Ar ion to a targetestablished in the negative electrode, discharging materials composingthe target with such collision energy, and laminating films ofapproximately the same composition as the target material on thesubstrate on the opposing positive electrode side.

[0004] The coating method employing the sputtering method ischaracterized in that it is capable of forming a thin film of angstromunits to a thick film of several ten μm at a stable deposition speed byadjusting the processing time, power supply, and so on.

[0005] A particular problem in forming an ITO film is the sputteringtarget density and generation of nodules during the sputteringoperation. The sputtering target for forming the ITO film is prepared bysintering the powder in which tin oxide powder and indium oxide powderare mixed at a prescribed ratio. Nevertheless, since this powder is oforiginally differing components and composition, the grain diameter ofsuch powder will vary, and it is inevitable that this powder will tendto be inferior at the stage of mixing in comparison to powders havingthe same component.

[0006] Nonetheless, since recent electronic devices are being furtherdownsized and miniaturized, the transparent conductive film itself isbeing thinly miniaturized, and, if such film is not formed uniformly,there is a trend of the influence on the deterioration of qualitybecoming great.

[0007] In consideration of the above, as a result of examining the poresinside the sintered body, it has become evident that tin oxide issegregated on the inner walls of the pores and the periphery thereof.And, one factor of such segregation being generated is that tin oxide,which is the ITO material, was aggregated.

[0008] Therefore, the improvement in the dispersibility of tin will leadto the reduction of pores, and it is anticipated that the effectivemanufacture of ITO sintered body targets with few generation of noduleswill become possible.

[0009] From this perspective, for the purpose of improving thedispersion status of tin, considered may be a method of premixing indiumsalt and tin salt, adding a precipitant to this mixed solution,simultaneously obtaining mixed sediments (coprecipitation method) viathe neutralization process of indium hydroxide and metastannate, anddrying, washing, sintering (oxidizing) this to obtain a mixed powder ofindium oxide and tin oxide.

[0010] Although this coprecipitation method, which is considered toimprove the dispersibility most efficiently, certainly makes thedispersibility of tin favorable, there is a problem in that theproduction cost will increase since there are numerous processes incomparison to ordinary manufacturing methods.

[0011] When the number of nodules on the erosion face of the ITO targetbecomes large, this induces irregular sputtering, and, in some cases,there is a problem in that an abnormal discharge or clustered(solidified) film will be formed, which may become a factor of a shortcircuit.

[0012] Simultaneously, oversized grains (particles) may float inside thesputtering chamber, and there is a problem in that this may similarlycause a short circuit in the thin film circuit by re-attaching on thesubstrate and cause protrusions on the thin film.

[0013] Accordingly, although it was necessary to obtain a high-densitysintered body target having uniform components, there was a problem inthat a manufacturing method of ITO powder and a manufacturing method ofan ITO target capable of satisfying these requirements and enabling lowmanufacturing costs could not be obtained.

DISCLOSURE OF THE INVENTION

[0014] The present invention was devised in order to solve the variousaforementioned problems, and, in particular, an object thereof is toprovide a manufacturing method of ITO powder and a manufacturing methodof an ITO target capable of obtaining a sintered body superior incomponent uniformity and favorable in forming ITO thin films byincreasing the dispersibility of tin and thereby reducing pores. It isthereby possible to provide at low costs ITO film forming powder and tinoxide—indium oxide target capable of restraining the deterioration ofquality or abnormal protrusions such as nodules in cases where the ITOsputtering target deposition in not uniform.

[0015] In order to overcome the foregoing problems, splay pyrolysis isused as the technical means, and ITO powder with tin dissolved in indiumoxide is manufactured thereby, and an ITO target is also manufactured asa result thereof. Thereby obtained was a discovery that ITO powder andtarget suitable for ITO transparent conductive films or the like couldbe obtained.

[0016] Based on the foregoing discovery, the present invention provides:

[0017] 1. A manufacturing method of ITO powder with tin dissolved inindium oxide, wherein the ITO powder is obtained by performing splaypyrolysis to a mixed solution or slurry of indium nitrate and tinchloride in which the concentration of indium and tin is 3.0 mol/L ormore;

[0018] 2. A manufacturing method of ITO powder with tin dissolved inindium oxide, wherein the ITO powder is obtained by performing splaypyrolysis to a mixed solution or slurry of indium nitrate and tinchloride in which the concentration of indium and tin is 4.0 mol/L ormore:

[0019] 3. A manufacturing method of ITO powder with tin dissolved inindium oxide according to paragraph 1 or paragraph 2 above, wherein thepowder is powder in which tin is supersaturatedly dissolved in indiumoxide;

[0020] 4. An ITO target manufacturing method, wherein the ITO target isobtained by preparing ITO powder upon performing splay pyrolysis to amixed solution or slurry of indium nitrate and tin chloride, recoveringthe ITO powder with tin dissolved in indium oxide pursuant to a filteror cyclone, and thereafter molding and sintering the ITO powder;

[0021] 5. An ITO target manufacturing method according to paragraph 4above, wherein the concentration of indium and tin in the mixed solutionor slurry of indium nitrate and tin chloride is 3.0 mol/L or more;

[0022] 6. An ITO target manufacturing method according to paragraph 4above, wherein the concentration of indium and tin in the mixed solutionor slurry of indium nitrate and tin chloride is 4.0 mol/L or more: and

[0023] 7. An ITO powder manufacturing method with tin dissolved inindium oxide according to each of paragraphs 4 to 6 above, wherein thepowder is powder in which tin is supersaturatedly dissolved in indiumoxide.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 are images showing the EPMA observation results ofpulverulent bodies in which the ITO powder of Example 1 was granulized;FIG. 2 are images showing the EPMA observation results of pulverulentbodies in which the mixed power of indium oxide and tin oxide ofComparative Example 1 was granulized; FIG. 3 are images showing the EPMAobservation results of pulverulent bodies in which the coprecipitatedITO powder of Comparative Example 2 was granulized; FIG. 4 are diagramsshowing the XRD measurement results of the respective pulverulent bodiesof Examples 1, 2 and Comparative Examples 1, 2; FIG. 5 is an SEMobservation image of the ITO powder of Example 3; and FIG. 6 is adiagram showing the XRD measurement results of the ITO powder of Example3.

BEST MODE FOR CARRYING OUT THE INVENTION

[0025] It is not as though there was no technology in the past formanufacturing indium oxide—tin oxide powder pursuant to splay pyrolysis(for example, Japanese Patent Laid-Open Publication No. S64-87519).Nevertheless, this was not manufactured for forming an ITO film withsputtering, and manufactured for forming a transparent conductive filmby applying ITO fine powder.

[0026] Therefore, as a specific example, splay pyrolysis is performedwith indium nitride and tin sulfate, and, here, the mixed solution to beused in the atomization is approximately 0.01 to several mol/L,preferably 0.5 to 2 mol/L. And, when it is too dense, it is recognizedthat fine powder cannot be obtained. This coincides with the technicalconcept in that sulfate, which does not dissolve easily, is used upondissolving tin.

[0027] Moreover, this technology is extremely inefficient in thatpulverulent bodies of pyrolysis gas containing vapor are recovered witha water scrubber, the ITO pulverulent bodies recovered in the water areleft still for three (3) days thereafter, and decantation andcentrifugation are performed thereto for the recovery.

[0028] Contrarily, with the present invention, ITO powder is obtained byperforming splay pyrolysis to a mixed solution or slurry of indiumnitride and tin chloride prepared such that the concentration of indiumand tin is 3.0 mol/L, and preferably 4.0 mol/L, wherein tin isdissolved, particularly supersaturatedly dissolved, in indium oxide.

[0029] Pyrolysis may be performed by employing a furnace which appliesheat with a flame method of direct atomization in the flame or anindirect method of electric heating. Pyrolysis can be suitably adjustedwithin a temperature range of 800° C. to 1200° C. for such heating.

[0030] A favorable sintered body ITO target cannot be manufactured whenthe concentration of indium and tin in the mixed solution of indiumnitride and tin chloride is less than 3 mol/L.

[0031] Preferably, dissolved (supersaturated) powder is obtained byemploying a mixed solution or slurry of 4 mol/L or more.

[0032] A precise sintered body ITO target superior in uniformityfavorable in ITO deposition can thereby be manufactured.

[0033] Further, when employing a slurry of indium nitride and tinchloride, although the liquidity will deteriorate, there is noparticular problem so as long as it will not hinder the atomization ofsuch slurry to the splay pyrolysis device. From this perspective, it isdesirable that the upper limit on the concentration of indium and tin beapproximately 8.0 mol/L.

[0034] The ITO powder with tin dissolved in indium oxide obtained byperforming splay pyrolysis to the mixed solution of indium nitride andtin chloride is recovered physically or mechanically with a back filter,stainless filter or cyclone.

[0035] Accordingly, processes such as wet-process decantation are nolonger necessary, and the ITO powder prepared by splay pyrolysis can beused as is. In other words, after recovering the ITO powder with tindissolved (supersaturated) in indium oxide, an ITO target is directlymanufactured by molding and sintering such recovered ITO powder.

EXAMPLES Comparative Examples

[0036] Examples of the present invention are now described. Further,these Examples are mere exemplifications, and the present invention isnot in any way limited thereby. In other words, the present inventioncovers modes and modifications other than these Examples based on thetechnical spirit of the invention.

Example 1

[0037] A solution in which indium metal was dissolved in a concentratednitric acid solution (60%) and a solution in which tin metal wasdissolved in hydrochloric acid (32%) were mixed such that the weightratio of In₂O₃:SnO₂ after splay pyrolysis becomes 9:1. Moreover, here,the concentration of indium+tin was made to be 4.64 mol/L in thesolution.

[0038] Next, this mixed solution was atomized and pyrolyzed with abinary fluid nozzle in a mullite core tube heated to 1000° C. Theatomization pressure was set to 0.2 Mpa, nozzle airflow rate to 25m³/min, carrier airflow rate to 20 m³/min, and concentrate solutionatomization amount to 1.6 kg/h. The produced ITO powder was recoveredwith a bug filter, and the pyrolyzed gas was recovered with a scrubber.The bug filter temperature was set to 180° C.

[0039] The obtained ITO powder had a specific surface area of 9.74 m²/g,a median size (D50) of 9.64 μm, and a bulk density of 0.34 g/cc.

[0040] Moreover, only In₂O₃ was observed with the XRD measurement of ITOpowder.

Example 2

[0041] A solution in which indium metal was dissolved in a concentratednitric acid solution (60%) and a metastannate slurry obtained bydissolving tin metal in hydrochloric acid (60%) were mixed such that theweight ratio of In₂O₃:SnO₂ after splay pyrolysis becomes 9:1. Moreover,here, the concentration of indium+tin was made to be 3.32 mol/L (382g/1) in the slurry.

[0042] Next, this slurry was atomized and pyrolyzed under the sameconditions as Example 1. The produced ITO powder was recovered with abug filter, and the pyrolyzed gas was recovered with a scrubber. The bugfilter temperature was set to 180° C.

[0043] The obtained ITO powder had a specific surface area of 10.03m²/g, a median size (D50) of 4.28 μm, and a bulk density of 0.23 g/cc.

[0044] Moreover, only In₂O₃ was observed with the XRD measurement of ITOpowder.

Comparative Example 1

[0045] Indium hydroxide was deposited by electrolyzing a solution inwhich indium metal was dissolved in a concentrated nitric acid solution(60%). This sediment was recovered with a filter press, washed, andthereafter dried and oxidized with a rotary kiln to obtain indium oxidepowder.

[0046] Simultaneously, metastannate prepared by dissolving tin metal ina concentrated nitric acid solution (60%) was recovered similarly with afilter press, washed, and thereafter dried and oxidized with a rotarykiln to obtain tin oxide powder.

[0047] The indium oxide and tin oxide were check-weighed such that theweight ratio thereof becomes 9:1, then mixed and pulverized with a beadmill to obtain indium oxide—tin oxide mixed (ITO) powder.

[0048] The obtained ITO powder had a specific surface area of 7.55 m²/g,a median size (D50) of 1.67 μm, and a bulk density of 0.65 g/cc.

[0049] Moreover, In₂O₃ and SnO₂ were observed with the XRD measurementof ITO powder.

Comparative Example 2

[0050] A mixed solution of indium salt and tin salt in which indiumoxide and tin oxide were mixed such that the ratio thereof becomes 9:1and a 25% ammonia aqueous solution were dripped while maintaining thereacting pH at 5.0 in order to obtain a sediment of indium and tin.

[0051] This sediment was filtered, and thereafter washed three timeswith purified water until the pH became 7.0. Next, this sediment wasdried at 120° C., and this dried substance was sintered for 40 minutesat 1100° C. while flowing hydrochloric gas of 20 vol %.

[0052] The obtained ITO powder had a specific surface area of 3.23 m²/g,a median size (D50) of 3.45 μm, and a bulk density of 0.58 g/cc.

[0053] Moreover, In₂O₃ and SnO₂ were observed with the XRD measurementof ITO powder.

Example 3

[0054] A solution in which indium metal was dissolved in a concentratednitric acid solution (60%) and a solution in which tin metal wasdissolved in hydrochloric acid (32%) were mixed such that the weightratio of In₂O₃:SnO₂ after splay pyrolysis becomes 9:1. Moreover, here,the concentration of indium+tin was made to be 4.64 mol/L in thesolution.

[0055] Next, 3 m³/h of butane, which is combustion gas, and 17 m³/hoxygen were injected to form an oxygen burner flame of approximately3000° C., and ITO atomized powder was prepared by atomizing theforegoing mixed solution (concentrate solution) in this flame.

[0056] The flow rate of the concentrate solution to be atomized in theflame was set to 8 kg/h, and oxygen gas was used as the carrier gas ofsuch concentrate solution in order to perform atomization at anatomization pressure of 0.2Mpa and flow rate of 5 m³/min.

[0057] The obtained ITO powder had a specific surface area of 1.07 m²/g,a median size (D50) of 0.86 μm, and a bulk density of 0.42 g/cc.

[0058] Moreover, as shown in FIG. 6, only In₂O₃ was observed with theXRD measurement of ITO powder.

[0059] Comparisons of the attributes of the ITO powder obtained inforegoing Examples 1, 2, 3 and Comparative Examples 1, 2 arecollectively shown in Table 1.

[0060] As shown in Table 1, the ITO powder prepared in aforementionedExample 1 and Example 2 have a large specific surface area in comparisonto the pulverulent bodies of Comparative Examples 1, 2, and is anaggregate of minute, uniform particles. The bulk density of thepulverulent bodies is small since the aggregation is comparativelygentle.

[0061] Meanwhile, with respect to Example 3, as shown with the SEMobservation image below, it has been confirmed that this is amonodispersive pulverulent body having extremely high crystallinity, andthat it is also a tin-supersaturated ITO powder of a single phase In₂O₃.TABLE 1 Specific Surface Median Size Bulk Density Area m³ · g⁻¹ μm g/ccXRD Example 1 9.74 9.64 0.34 In₂O₃ Single Phase Example 2 10.03 4.280.23 In₂O₃ Single Phase Comparative 7.55 1.67 0.65 In₂O₃ + Example 1SnO₂ Comparative 3.23 3.45 0.58 In₂O₃ + Example 2 SnO₂ Example 3 1.070.86 0.42 In₂O₃ Single Phase

[0062] EPMA observation images of pulverulent bodies in which the ITOpowder of Example 1 was granulized are shown in FIG. 1(A, B); EPMAobservation images of pulverulent bodies in which the mixed power ofindium oxide and tin oxide of Comparative Example 1 was granulized areshown in FIG. 2(A, B); and EPMA observation images of pulverulent bodiesin which the coprecipitated ITO powder of Comparative Example 2 wasgranulized are shown in FIG. 3(A, B), respectively.

[0063] It has been observed that tin is dispersed uniformly in Example 1shown in FIG. 1(A). Although not shown, similar results were obtained inExample 2 as those shown in FIG. 1.

[0064] Contrarily, it has been observed that tin is partially segregatedin the Comparative Example of FIG. 2(A). It is thereby possible toconfirm that the splay pyrolysis of the present Examples improves thedispersibility of tin in comparison to Comparative Example 1.

[0065] Further, in the EPMA observation of FIG. 3, obtained were resultsin which the dispersibility of tin appears to be the same as the splaypyrolysis shown in FIG. 1.

[0066] The XRD measurement results of Examples 1, 2 and ComparativeExamples 1, 2 are shown in FIG. 4. The upper graph in FIG. 4 shows theXRD measurement results of ITO powder of Examples 1, 2, and the lowergraph shows the XRD measurement results of ITO powder of ComparativeExamples 1, 2.

[0067] As shown in FIG. 4, although the peak of SnO₂ of the pulverulentbodies of Comparative Examples 1, 2 can be observed at around 26.5degrees, this peak does not appear in Examples 1, 2, and it is evidentthat SnO₂ is dissolved in In₂O₃.

[0068] Thereby, with the ITO powder of Examples 1, 2, tin is dissolvedin the indium oxide matrix, and it is evident that the improvement inthe dispersibility of tin is pursuant to the dissolution of tin.

[0069] As described above, with the EPMA observation in thecoprecipitated powder of Example 2, although the dispersibility of tinappeared to the same as splay pyrolysis, it is clear that tin is notdissolved upon viewing this XRD.

[0070] Further, FIG. 5 is an SEM observation image of the ITO powder ofExample 3, and FIG. 6 is a diagram showing the XRD measurement resultsof such ITO powder. It is clear from these diagrams that the ITO powderof Example 3 is a tin-supersaturated ITO powder of single phase In₂O₃,and that it is a monodispersive pulverulent body with highcrystallinity. The dispersibility of tin is thereby significantlyimproved.

[0071] As illustrated in foregoing Examples 1 to 3, it is evident thatthe splay pyrolysis of the present invention is considerably superior inthe dispersibility of tin.

EFFECT OF THE INVENTION

[0072] Provided is a manufacturing method of ITO powder suitable inmanufacturing an ITO sputtering target by increasing the dispersibilityof tin and thereby reducing pores. It is thereby possible to restrainthe deterioration of quality or abnormal protrusions such as nodules incases where the ITO sputtering target deposition is not uniform.

1. A manufacturing method of ITO powder with tin dissolved in indiumoxide, wherein said ITO powder is obtained by performing splay pyrolysisto a mixed solution or slurry of indium nitrate and tin chloride inwhich the concentration of indium and tin is 3.0 mol/L or more.
 2. Amanufacturing method of ITO powder with tin dissolved in indium oxide,wherein said ITO powder is obtained by performing splay pyrolysis to amixed solution or slurry of indium nitrate and tin chloride in which theconcentration of indium and tin is 4.0 mol/L or more.
 3. A manufacturingmethod of ITO powder with tin dissolved in indium oxide according toclaim 1 or claim 2, wherein said powder is powder in which tin issupersaturatedly dissolved in indium oxide.
 4. An ITO targetmanufacturing method, wherein said ITO target is obtained by preparingITO powder upon performing splay pyrolysis to a mixed solution or slurryof indium nitrate and tin chloride, recovering the ITO powder with tindissolved in indium oxide pursuant to a filter or cyclone, andthereafter molding and sintering said ITO powder.
 5. An ITO targetmanufacturing method according to claim 4, wherein the concentration ofindium and tin in the mixed solution or slurry of indium nitrate and tinchloride is 3.0 mol/L or more.
 6. An ITO target manufacturing methodaccording to claim 4, wherein the concentration of indium and tin in themixed solution or slurry of indium nitrate and tin chloride is 4.0 mol/Lor more.
 7. An ITO powder manufacturing method with tin dissolved inindium oxide according to each of claims 4 to 6, wherein said powder ispowder in which tin is supersaturatedly dissolved in indium oxide.